So I still have kio_sftp problems communicating with servers. I opened up a bug report, but it has gotten no traction. This is a problem that is reproducible on multiple machines in exactly the same steps. Notably, the same problem does NOT happen using kio_sftp with Kate's file open/save dialog.

Basically, after four clicks around to /new/ locations (nothing cached) Dolphin locks up saying "Loading folder...". If I press the back button, everything shows up. If I go to a place I've gone before it shows up, but if I go to a new fifth place it won't go.

See: Bug 364642 - 16.04.3: kio_sftp is broken

edit: I have shared keys to the server, and I access the server via sftp://serverName/my/folder in Dolphin's URL bar.